In the field of medical imaging systems it is generally known to combine different images of a patient acquired by identical or different medical analysis systems in order to improve the diagnostic possibilities. In particular, ultrasound systems are known which combine ultrasound images with pre-operative image data of a patient derived from different imaging systems.
Ultrasound imaging systems can further combine predefined models of the anatomical structure scanned by the ultrasound probe or segmentation data with the images derived from the acquired ultrasound data in order to provide segmented images on the basis of the anatomical model and the ultrasound image data. A corresponding system is e.g. known from US 2012/0065510 A1.
During an ultrasound image assisted medical procedure such as a biopsy and/or branchytherapy, a real-time image and a corresponding real-time segmentation of anatomical objects i.e. a definition of a volume or a surface of an anatomical object in the field of view of the ultrasound probe can provide several advantages.
Conventional anatomical segmentation techniques require a clear contrast between different tissues visible in the provided image data such as magnet resonance tomography (MRT) or computer tomography (CT). However a majority of the known segmentation techniques have a reduced performance for ultrasound imaging systems, since the segmentation model cannot properly be aligned to the ultrasound images which have a poor signal-to-noise ratio. Usually a prior information about the shape of the anatomical structure to be segmented can improve the segmentation of the anatomical structures in the ultrasound images and these techniques are typically applied to three-dimensional data which require a large computation effort so that these techniques are typically expensive and cannot be applied to real-time applications.
In some further known biopsy and/or branchytherapy applications two-dimensional image data is acquired and on the basis of a position sensor reconstructed into a regular three-dimensional voxel array which is used for segmentation of anatomical objects.
The disadvantage of the known techniques for segmenting anatomical objects in ultrasound image data is that the previously determined three-dimensional segmentation models do not consider deformation of the anatomical objects during the analysis. The computational effort for aligning the segmentation model to real-time three-dimensional ultrasound image data makes three-dimensional segmentation in real-time during the intervention difficult. Furthermore, acquiring three-dimensional data during the intervention is complex so that typically only two-dimensional data is acquired during the intervention.